terminal: KAM (mode 2)

This has an associated config `vt-kam-allowed` which defaults to "false"
since this mode can cause the terminal to become mostly unusable. We
include this mode for completions sake however.

src/Surface.zig

@@ -145,6 +145,7 @@ const DerivedConfig = struct {
     mouse_shift_capture: configpkg.MouseShiftCapture,
     macos_non_native_fullscreen: configpkg.NonNativeFullscreen,
     macos_option_as_alt: configpkg.OptionAsAlt,
+    vt_kam_allowed: bool,
     window_padding_x: u32,
     window_padding_y: u32,
 
@@ -166,6 +167,7 @@ const DerivedConfig = struct {
             .mouse_shift_capture = config.@"mouse-shift-capture",
             .macos_non_native_fullscreen = config.@"macos-non-native-fullscreen",
             .macos_option_as_alt = config.@"macos-option-as-alt",
+            .vt_kam_allowed = config.@"vt-kam-allowed",
             .window_padding_x = config.@"window-padding-x",
             .window_padding_y = config.@"window-padding-y",
 
@@ -985,6 +987,13 @@ pub fn keyCallback(
         if (consumed and performed) return true;
     }
 
+    // If we allow KAM and KAM is enabled then we do nothing.
+    if (self.config.vt_kam_allowed) {
+        self.renderer_state.mutex.lock();
+        defer self.renderer_state.mutex.unlock();
+        if (self.io.terminal.modes.get(.disable_keyboard)) return true;
+    }
+
     // If this input event has text, then we hide the mouse if configured.
     if (self.config.mouse_hide_while_typing and
         !self.mouse.hidden and

src/config/Config.zig

@@ -461,6 +461,14 @@ keybind: Keybinds = .{},
 /// The default value is "16-bit".
 @"osc-color-report-format": OSCColorReportFormat = .@"16-bit",
 
+/// If true, allows the "KAM" mode (ANSI mode 2) to be used within
+/// the terminal. KAM disables keyboard input at the request of the
+/// application. This is not a common feature and is not recommended
+/// to be enabled. This will not be documented further because
+/// if you know you need KAM, you know. If you don't know if you
+/// need KAM, you don't need it.
+@"vt-kam-allowed": bool = false,
+
 /// If anything other than false, fullscreen mode on macOS will not use the
 /// native fullscreen, but make the window fullscreen without animations and
 /// using a new space. It's faster than the native fullscreen mode since it

src/terminal/modes.zig

@@ -170,6 +170,7 @@ const ModeEntry = struct {
 /// valuable to redocument them all here.
 const entries: []const ModeEntry = &.{
     // ANSI
+    .{ .name = "disable_keyboard", .value = 2, .ansi = true }, // KAM
     .{ .name = "insert", .value = 4, .ansi = true },
 
     // DEC

website/app/vt/modes/kam/page.mdx

@@ -0,0 +1,28 @@
+import VTMode from "@/components/VTMode";
+
+# Keyboard Action Mode (KAM)
+
+<VTMode value={2} ansi={true} />
+
+Disable all keyboard input.
+
+This mode is unset as part of both [full reset (RIS)](/vt/ris)
+and [soft reset (DECSTR)](/vt/decstr).
+
+A poorly behaved terminal program can lock the terminal emulator
+using this command. Terminal emulators should provide a mechanism
+to reset this or outright disable it.
+
+## Validation
+
+### KAM V-1: Disable Keyboard Input
+
+```bash
+printf "\033[1;1H" # move to top-left
+printf "\033[0J" # clear screen
+printf "Keyboard input is now disabled.\n"
+printf "\033[2h"
+sleep 5
+printf "\033[2l"
+printf "Keyboard input is re-enabled.\n"
+```

website/components/VTMode.tsx

@@ -0,0 +1,18 @@
+export default function VTMode({
+  value,
+  ansi = false,
+}: {
+  value: number;
+  ansi: boolean;
+}) {
+  return (
+    <div className="flex my-2.5">
+      <div className="border px-1 grid grid-rows-2 grid-cols-1 text-center">
+        <div>
+          {ansi ? "?" : ""}
+          {value}
+        </div>
+      </div>
+    </div>
+  );
+}